1. Field of the Invention
The present invention relates to a recording thin film magnetic head used with, for example, a flying magnetic head and, more particularly, to a thin film magnetic head adapted to reduce inductance and capable of handling higher recording frequencies, and a manufacturing method for the same.
2. Description of the Related Art
FIG. 27 is a partial front view showing a construction of a conventional thin film magnetic head or inductive head, and FIG. 28 is a partial sectional view of the thin film magnetic head cut along the line XXVIII—XXVIII shown in FIG. 27 and viewed from the direction of an arrow.
Reference numeral 1 shown in FIGS. 27 and 28 denotes a lower core layer formed of a magnetic material, such as Permalloy. An insulating layer 9 is deposited on the lower core layer 1.
The insulating layer 9 includes a groove 9a having an inner width represented by a track width Tw, the groove 9a extending in a height direction or Y direction in the drawing, from a surface facing a recording medium (hereinafter referred to as “ABS” which stands for air bearing surface).
In the groove 9a, a lower magnetic pole layer 3 magnetically connected to the lower core layer 1, a gap layer 46, and an upper magnetic pole layer 5 magnetically connected to an upper core layer 48 are deposited by sequentially plating in this order from bottom.
Referring to FIG. 28, a spirally formed coil layer 7 is provided on the insulating layer 9 in a portion in the height direction or the Y direction in the drawing from the groove 9a formed in the insulating layer 9.
The coil layer 7 is covered by a coil insulating layer 47 formed of a resist or the like, and an upper core layer 48 is deposited on the coil insulating layer 47. The upper core layer 48 is magnetically connected with the upper magnetic pole layer 5 at a distal end portion 48a and also magnetically connected to the lower core layer 1 at a proximal end portion 48b. 
In the inductive head shown in FIGS. 27 and 28, when recording current is supplied to the coil layer 7, a recording field is induced in the lower core layer 1 and the upper core layer 48. Magnetic signals are recorded in a recording medium, such as a hard disc, by a leakage field from between the lower magnetic pole layer 3 magnetically connected to the lower core layer 1 and the upper magnetic pole layer 5 magnetically connected to the upper core layer 48.
In the inductive head shown in FIGS. 27 and 28, a lower magnetic pole layer 3 locally formed over the track width Tw, the gap layer 46, and the upper magnetic pole layer 5 are provided in the vicinity of the surface facing the recording medium. This type of inductive head permits a narrower track.
The following will describe a manufacturing method for the inductive head shown in FIGS. 27 and 28. First, the insulating layer 9 is deposited on the lower core layer 1, then the groove 9a having the track width Tw is formed in the insulating layer 9 for a predetermined length in the height direction (depth direction) from the surface facing the recording medium (air bearing surface).
In the groove 9a, the lower magnetic pole layer 3, the gap layer 46, and the upper magnetic pole layer 5 are continuously plated, then the coil layer 7 is pattern-deposited on a portion of the insulating layer 9 that is located behind (in the height direction) from the groove 9a formed in the insulating layer 9.
The coil layer 7 is covered by a coil insulating layer 47, and the upper core layer 48 is formed from the top of the upper magnetic pole layer 5 to cover the coil insulating layer 47 by the flame plating process. This completes the inductive head shown in FIGS. 27 and 28.
For a trend toward higher recording densities and higher recording frequencies, it is necessary to reduce a track width and the inductance of an inductive head.
In order to reduce inductance, a magnetic path formed via the upper core layer 48 from the lower core layer 1 must be made shorter. This requires that a width T1 of the coil layer 7 formed from the distal end portion 48a to the proximal end portion 48b of the upper core layer 48 be reduced. Reducing the width T1 of the coil layer 7 allows the upper core layer 48 to be shortened so as to achieve a shorter magnetic path.
A method for forming the coil layer 7 by two layers could be applied to decrease the width T1 of the coil layer 7 without changing the number of turns of the coil layer 7.
In the construction of the thin film magnetic head shown in FIGS. 27 and 28, however, the magnetic path cannot be made sufficiently shorter to be able to handle higher recording frequencies in the future merely by providing the coil layer 7 with the double-layer construction. This makes it difficult to achieve an appropriate reduction in inductance.
A reason for the difficulty mentioned above is that the coil layer 7 is deposited on the insulating layer 9 having a thick film. Referring to FIG. 27, the insulating layer 9 has a film thickness H5, and the film thickness H5 is larger than or substantially identical to a total film thickness H6 of the lower magnetic pole layer 3, the gap layer 46, and the upper magnetic pole layer 5. Therefore, as shown in FIG. 28, when a junction surface between the upper magnetic pole layer 5 and the upper core layer 48 is defined as a reference plane, the coil layer 7 deposited on the insulating layer 9 is positioned more closely to the upper core layer 48 than the reference plane.
Hence, adopting the double-layer construction directly to the coil layer 7 would lead to an extremely large height from the upper surface of the lower core layer 1 to the upper surface of the coil insulating layer 47 covering the coil layer 7 even though the width T1 of the coil layer 7 can be reduced. As a result, the magnetic path cannot be shortened much, making it impossible to accomplish an appropriate reduction in inductance.
If the double-layer construction is simply applied to the coil layer 7 in the inductive head having the construction illustrated in FIG. 28, then a thickness H1 of the coil insulating layer 47 covering the coil layer 7 increases, resulting in an extremely large bulge of the coil insulating layer 47 when the upper surface of the upper magnetic pole layer 5 is defined as the reference plane.
Accordingly, it becomes difficult to pattern-form the upper core layer 48 from above the upper magnetic pole layer 5 to cover the coil insulating layer 47 by the flame plating process, posing a problem in that a portion in the vicinity of the distal end portion 48a of the upper core layer 48 cannot be formed into a predetermined shape.
If the width T2 of each conductor of the coil layer 7 is decreased, and a height H2 of each conductor is increased, then there should be no change in the volume of the coil layer, thus avoiding an increase in a coil resistance value. Furthermore, in this case, since the width T2 of each conductor can be reduced, the width T1 of the entire coil layer 7 can be reduced, permitting a further reduction in inductance by making a magnetic path even shorter.
On the other hand, however, another problem arises in that the increased height H2 of each conductor inevitably leads to an even larger bulge of the coil insulating layer 47 covering the coil layer 7, preventing the upper core layer 48 from being formed with high accuracy.